As wireless mobile communications evolve rapidly, various wireless communication systems such as 4G/5G mobile communication terminals, wireless control systems, Machine to Machine (M2M), and Internet of Things (IoT) require elements which are more lightweight, have a simple structure, and are miniaturized into a structure that facilitates integration.
Accordingly, various schemes for reducing a physical size of a circuit have been studied, and flat microwave elements and circuits have been widely developed and applied because they are easy to design and manufacture.
In particular, manufacturers of mobile communication terminals and wireless control systems in the world require a miniaturized, flexible, broadband, high-gain antenna which is operated at a low power with high radiation efficiency and has no spatial constraints when mounted in a circuit.
As miniaturization schemes for such an antenna, various schemes such as a scheme of applying a helical structure and a scheme of applying a meta-material and a stacked structure are applied.
Among the above schemes, since a resonance frequency is generated per one rotation around a circumference, the helical structure is not suitable for a scheme of miniaturizing an antenna having a single resonance frequency characteristic. In addition, schemes of applying the meta-material and the stacked structure have a disadvantage in that a configuration is complicated and a manufacturing cost is increased.
In addition, the technology utilizing a basic Moebius strip having a three-dimensional structure and the technology of a flat structure utilizing a characteristic of a Moebius strip have been proposed. However, the above flat structure is not a perfect flat structure, and a line coupling effect occurs at a low frequency.
An example of such broadband monopole antenna technology according to the related art is disclosed in Korean Patent Registration No. 10-0416883 (issued on Feb. 5, 2004), Korean Patent Registration No. 10-0660051 (issued on Dec. 22, 2006), etc.